(i) Field of the Invention
This invention relates to novel phosphoric esters and more particularly, to phosphoric esters of the general formula (I) ##STR2## in which R.sub.1 represents a saturated or unsaturated, linear or branched and substituted or unsubstituted hydrocarbon group having from 8 to 32 carbon atoms, R.sub.2, R.sub.3 and R.sub.4 are the same or different and represent a saturated or unsaturated hydrocarbon group having from 1 to 4 carbon atoms, R.sub.5 represents a hydrogen atom a saturated or unsaturated hydrocarbon group having from 1 to 4 carbon atoms, and n is an integer of from 0 to 56.5.
The invention also relates to a method for preparing the phosphoric acids of the type indicated above.
(ii) Description of the Prior Art
As phosphoric esters having quaternary ammonium salts in one molecule thereof, there are known phospholipids, typical of which is natural lecithin. These phospholipids have surface activity, emulsifiability and physiological characteristics and are thus used in various fields.
A number of substances are currently used as detergents, including alkylsulfates, polyoxyethylene alkylsulfates, alkylbenzenesulfonates, alphaolefinsulfonates, monoalkyl phosphates, acylglutamic acid salts, and the like. These surface active agents, in most cases, bring about chapping of skin. For the purpose of low skin irritations, there are now used monoalkyl phosphates and acylglutamic acid salts.
As is well known, a number of phosphoric ester derivatives such as phospholipids exist in living body, so that it will be expected that substances having structures similar to those of phosphoric ester derivatives, e.g. phosphoric esters having quaternary ammonium salts in one molecule thereof, have low irritations against living body.
However, it is usually very difficult to prepare phospholipids: the preparation generally needs a number of steps, resulting in a low yield of an intended product (see, for example, E. Baer et al; J. Amer, Chem. Soc. 72, 942(1950), and "Lipids" edited by Tamio Yamakawa and published by Kyoritsu Pub. Co., Ltd. (1973)).
The results of several studies on synthesis of compounds having structures similar to those structures of phospholipids have been reported. However, these reactions comprise a number of complicate steps, or may, in some cases, need starting materials which are difficult to prepare. Alternatively, an intended product obtained after the reaction may often be very difficult to separate and yield of which is low. In addition, final products have not necessarily adequate surface activity (see, for example, Japanese Patent Publication Nos. 42-23330 and 48-1654, and U.S. Pat. No. 3507937).